1. Identify in the circuit

         Zener diodes are often represented by "ZD" plus a number in the circuit. For example: ZD1 represents the Zener diode numbered 1.

         2. Identification of positive and negative poles

         From the appearance point of view, the positive end of the metal package Zener diode body is flat and the negative end is semicircular. One end with the color mark printed on the plastic Zener diode body is the negative pole, and the other end is the positive pole. For zener diodes whose markings are unclear, you can also use a multimeter to determine their polarity. The measurement method is the same as for ordinary diodes.

         3. Color ring Zener diode identification

         The color ring on the color ring Zener diode represents two meanings: one represents the number, and the other represents the number of decimal points (usually the color ring Zener diode takes one decimal place and is represented by brown. It can also be understood as the magnification: ×10 (-1 power), the number corresponding to the specific color is the same as the color ring resistance).

         4. Differentiation from ordinary rectifier diodes

        First, use the R×1K scale of the multimeter to judge the positive and negative electrodes of the tube under test. Then set the multimeter to the R×10K block, connect the black test lead to the negative electrode of the tube under test, and the red test lead to the positive electrode of the tube under test. If the reverse resistance value measured at this time is greater than the reverse resistance measured with the R×1K block If it is much smaller, it means that the tube under test is a voltage regulator tube; on the contrary, if the measured reverse resistance value is still very large, it means that the tube is a rectifier diode or a detector diode.